The invention relates to a process for the manufacture of a complex moulded structure. It also relates to the complex moulded structures and especially to the skis thus obtained.
By "complex moulded structure" is traditionally meant a moulded structure containing:
stiffening or reinforcing elements being in the form of wires or in the form of cloths, or even in the form of plates, PA1 and, possibly, protection elements, PA1 and/or various mechanical elements such as, for example, damping elements, lightening elements, etc. PA1 and, possibly, decoration elements. PA1 depositing in a mould a first element intended to form the lower half-shell, PA1 depositing on this first element a deformable tubular element; PA1 depositing on this deformable tubular element a second element intended to form the upper half-shell; PA1 closing the mould; PA1 injecting into the deformable tubular element reactants intended to react in order to form a foam which expands in situ until pressing the element against the walls of the mould; PA1 cooling the contents of the mould, PA1 and finally opening the mould in order to withdraw the complex moulded structure thus obtained.
Within the scope of the production of such structures, one of the main concerns consists in seeking a process capable of permitting a high degree of automation whilst optimizing the technical and mechanical characteristics of the final structure obtained.
Among the various processes known to date for the production of such structures, one of them consists in using the pressure caused by the expansion of a foam made from plastic, especially from polyurethane, in order for the various elements entering in the composition of the structure to be pressed against the interior walls of a shaping mould (see for example French Patent FR-A-2,553,669).
Now, in general, and especially in the framework of the application to skis, use is frequently made, as stiffening and/or reinforcing element, of textile materials in the form of cloths advantageously preimpregnated with a solventless resin, which during the production of the structure develops adhesive properties, especially in contact with the central core.
Now the use of a central core of the polymerizable foam type in association with such a preimpregnated reinforcing element comes up against a major difficulty: in fact, incompatibility or, on the contrary, affinity phenomena sometimes arise between the constituent elements of the foam of the central core and the constituent elements of the resin for impregnating the preimpregnated fabric, leading to local alterations in the cohesion of the structure, unacceptable for numerous applications and especially for a ski. These phenomena may induce adhesion defects between these two elements, leading to a structure being obtained which is imperfect from the point of view of its mechanical properties.
In document FR-A-1,248,660, it has been proposed, for the production of such a structure, to install an air chamber in the mould, then to inflate this air chamber by means of compressed air, the result of which presses the constituent elements of the structure against the walls of the mould, and finally to inject a polymerizable foam into the space thus provided.
Although for sure this process enables previously mentioned drawbacks to be overcome, on the other hand it requires at least two steps, namely the inflation of the air chamber and then the injection of the reactants of the core, therefore longer to implement and furthermore relatively difficult to be able to be automated.